This case study introduces interactive sonification to evolutionary strategies (ES) for global optimization. We briefly describe the specific strengths of sonification as a tool for monitoring, the emerging trend of interactive sonification, and what it can add to the field of evolutionary computation. Then we line out the background of ES as optimization heuristics, briefly explain the algorithmic procedure of ES and discuss the need to intervene during optimization runs and the current shortcomings in appropriate user feedback. This motivates the development of an auditory closed loop setup that brings the expertise of interactive sonification to the field of monitoring ES algorithms. Further, we present considerations for the sound design and the detailed mapping of parameters from the ES to sound properties. Finally, we discuss the various implemented modes of interaction and their significance for the optimization through ES.